The invention relates to a fibreboard formed of a fibrous tissue by dry forming in a forming box and with subsequent fixing of fibres by heat treatment in an oven, wherein the fibres are selected from synthetic fibres, natural fibres or a mixture thereof, wherein the fibreboard consists of at least one layer of said fibres, wherein the thickness of the fibreboard and the density are adapted to the actual use, and wherein the fibreboard has rupture zones perpendicular to the surface of the fibreboard.
The invention also relates to a forming box for use in the manufacture of fibreboards formed of a fibrous tissue by dry forming in a forming box and with subsequent fixing of fibres by heat treatment in an oven, wherein the fibres are synthetic fibres, natural fibres or a mixture thereof, and wherein the forming box is arranged above a forming wire which extends across a vacuum box.
Danish Patent Application No. 1520/97, EP Patent Application No. 0 159 618 and U.S. Pat. No. 05,445,777 disclose various types of machines for the manufacture of boards of fibrous tissue. It is common to the known types of machines that all of them distribute fibres of some type so as to form a board-shaped fibrous tissue. The fibres are divided by rollers or other means constructed so that the fibres are distributed evenly and do not lump. These means may be constructed in many different ways, but all the machines are unique in that they are part of equipment that is used in the manufacture of boards, mats or sheets of relatively homogeneous fibrous tissue.
The object of the invention is to introduce rupture zones in the fibreboards, where rupture zones are formed directly in the forming process in such a manner that there are no through-going fibres in the rupture zone gap, and that the gap of the rupture zone is formed without the use of cutting tools.
Fibreboards are taken to mean boards made of fibres, such as e.g. insulation boards or insulation mats.
The fibreboard may be formed with rupture zones which extend in at least one direction, wherein the rupture zones consist of a gap having a height of between 10% and 100% of the thickness of the fibreboard, and wherein the forming of the fibreboard of a fibrous tissue directly provides rupture zones which do not have through-going fibres in the gap of the rupture zone, thereby forming a rupture zone gap without the use of cutting tools. The rupture zones ensure that the fibreboard/insulation mat may be adapted to the desired size within given intervals without the use of tools, since there are no through-going fibres in the rupture zone gaps. The fibrous tissue is kept together in the gaps as an effect of the heat treatment. At the same time, separation of the fibreboard results in a regular rupture face and optimum engagement face with any adjoining elements or adjoining fibreboards.
This facilitates handling of the product, since no tool of any type has to be used for performing an adaptation of the fibreboard/insulation mat. The regular rupture face ensures that a so-called thermal bridge is not created at the joint, that is an optimum insulation capacity is maintained at the joint.
The fibreboard may be made with rupture zones which extend in the longitudinal direction of the fibreboard as well as in transverse direction of the fibreboard. Rupture zones longitudinally of and transversely to the fibreboard make it easy to adapt the board in length as well as in width prior to final arrangement of the board.
The fibreboard may be made with a given distance between two rupture zones or between the rupture zone and the edge of the fibreboard in the order of up to half the board width. This provides the possibility of achieving a product which can be adapted in size within selected intervals easily and without difficulty.
The fibreboard may be made of natural fibres, such as animal hair, fibres from flax, hemp, jute, ramie, sisal, cotton, kapok, glass, stone, cellulose, newspaper, elephant grass, sphagnum, seaweed, palm fibres or the like.
All of these fibres have a certain insulating capacity that may be useful in various situations. Furthermore, it is possible to grow some of the mentioned vegetable fibres on ordinary agricultural areas.
The fibreboard may also be made of synthetic fibres, such as polyamide, polyester, polyacrylic, polypropene, two-component fibres or the like. Fibreboards made of synthetic fibres that can easily be adapted without the use of tools, may mean in the industry that a cutting step may be avoided in the production of e.g. diapers.
The fibreboard may also be made of a mixture of natural fibres and synthetic fibres, which involves the same advantages as mentioned above.
The fibreboard may moreover contain a fire-resistant substance. For example, it may be mentioned that the addition of ammonium phosphate can give the desired fire-resistant effect. It may be a requirement from various authorities that the product can withstand a specified fire test. Some of the mentioned fibres per se have a partial fire resistant property, while others require additional protection. Addition of a fire resistant substance, where necessary, provides optimum properties.
The forming box may be provided with at least one vertical partition which extends in the direction of movement of the forming wire and thereby essentially divides the forming box longitudinally, and wherein a set of vertical partitions are introduced transversely to the direction of movement of the forming wire and, in individual lengths, essentially correspond to the distance between the longitudinal partitions, said sets of transverse partitions being moved in the same direction and at the same rate as the forming wire, wherein the distance between the transverse sets of partitions is variable, and wherein the height of the transverse partitions is between 10% and 100% of the thickness in which the apparatus is set to produce the fibreboard, and wherein the forming box is constructed such that any fibres intended for the manufacture of fibreboards and adhering to the upper edge of the partition may be removed by movable means.
That the partitions are mounted longitudinally of the forming box in the direction of movement of the forming wire and transversely to the forming wire, respectively, in such a manner that the transverse partitions are advanced at the rate of the forming wire, means that it is possible to manufacture fibreboards/insulation mats with incorporated rupture zones in two directions for easier handling.
The forming box may be constructed such that any fibres intended for the manufacture of fibreboards and adhering to the upper edge of a partition, are removed by at least one rotating roller provided with radially mounted spikes.
The rotating rollers ensure that fibres do not accumulate on the upper edge of the partitions. If fibres adhere to the edges of the partitions, it may result in non-uniform distribution of fibres in the forming box.
The longitudinal partitions of the forming box may be mounted so as to provide a distance A between partition and forming wire, the size of the distance A being variable between 0% and 100% of the thickness of the fibreboard.
When this distance is greater than 0% of the thickness of the fibreboard, fibres are allowed to form a coherent lower layer on the fibreboard. This layer, together with the heat treatment, contributes to keeping the fibreboard/insulation mat together. At a distance A which is 0% of the thickness of the fibreboard, it is solely the effect of the heat treatment that keeps the fibreboard together around its rupture zones.
The forming box may have longitudinal partitions constructed such that the fibrous tissue on at least one of the outer sides of the fibreboard is not affected by partitions. This provides a coherent fibre layer on at least one side of the fibreboard. This coherent layer and the subsequent heat treatment impart additional stability to the fibreboard/insulation mat.
The forming box may also have transverse partitions constructed such that the fibrous tissue on at least one of the outer sides of the fibreboard is not affected by partitions. This also provides a coherent fibre layer on at least one side of the fibreboard.
Furthermore, the partitions of the forming box may be constructed such that the produced fibrous tissue is formed in two or more independent webs, or in a plurality of independent sections. This means that in some cases a cutting process is no longer necessary. The production apparatus can now merely be adjusted to the desired division. For example, insulation mats may be produced in a finished size without subsequent final trimming of edges or the like.
The longitudinal partitions of the forming box may be adjustable in number and in mutual distance, and the partitions may be adjustable in the direction of their height as well as in the direction of their length. Likewise, the transverse partitions of the forming box may be adjustable in number, in mutual distance and in height. This ensures great flexibility with respect to how the rupture zones may be formed longitudinally of and transversely to the fibreboard.